UA121483C2 - Method for controlling an oil-injected compressor device - Google Patents

Abstract

Method for controlling a compressor device (1) with a compressor element (2) and oil circuit (14) with oil (15) that is injected into the compressor element (2) by a fan (19) via a cooler (18), with a bypass pipe (20) across the cooler (18), whereby when the temperature (T) of the compressor element (2) is less than a value (Tset) the method consists of taking the following steps: - the fan (19) is switched off; - when the temperature (T) is still less than T«,, the oil (15) is driven via the bypass pipe (20); - when the temperature (T) is still less than Tset, the quantity of oil (15) that is injected into the compressor element (2) is decreased until the temperature (T) is equal to Tset.

Description

The invention relates to a method of regulating a compressor device with oil injection.

More specifically, the invention is directed to an oil-injected compressor device having at least one compression element with an inlet for the gas to be compressed and an outlet for the compressed gas, the compressor device having an oil circuit with an oil separator with an inlet connected thereto with the outlet of the compression element, and with the outlet to which the consumer of the compressed gas network can be connected, while this oil separator contains a pressure tank in which the oil is separated from the resulting compressed gas and from which the oil can be sent to the cooler, and then can be injected into the compression element, and this cooler is cooled by a refrigerant that is directed through the cooler by a fan or pump.

It is known that to change the speed of the flow that such a compressor unit supplies, the speed of the compression element can be changed by a regulator that can change the speed.

As the speed of the compression element decreases, the delivered flow will also decrease.

The speed of the compression element cannot fall indefinitely, and it is limited to a certain lower limit.

This means that the flow rate cannot be reduced without any limitation.

If the flow must be further reduced, it can be selected using an inlet throttle valve.

The use of such an inlet throttle valve is known in compressor installations, where the compression element is driven at a constant speed.

In order to throttle the input, a rotary valve is used, which, for example, is attached to the intake pipe.

This will create a partial overlap of the inlet pipe and thus the flow of the supplied gas will be blocked and therefore the flow rate will also be reduced.

The use of an inlet throttle valve in a compressor unit with a variable speed compression element has been impossible in the past or impractical to implement.

Due to the reduction in the velocity of the supplied flow as a result of throttling, less power will need to be spent on the compression element.

As a result, less heat will be generated, which can lead to problems, as the temperature of the compressor unit becomes too low.

After all this, it is necessary to keep the temperature within certain limits, because at a very low temperature condensation can occur, which can lead to problems throughout the machine, and at a very high temperature, the oil used for cooling and lubrication will deteriorate more quickly.

Methods are already known to ensure that the oil temperature in an oil-injected, constant-speed compressor unit does not become too low to prevent oil condensation.

Such a known method, described in (MO 2007/045052| by the same applicant), in which a bypass pipe is installed on the oil cooler and temperature regulator, which ensures that when the oil temperature threatens to become too low, at least part of the oil for injection is directed in whole or in part along the coolant is passed directly to the compression element without cooling.

In this case, the compression element and the fan used to cool the oil in the cooler both continue to run at a constant speed from the heat engine, even when no cooling is required, if the oil is completely or partially diverted through the bypass pipe, resulting in energy loss.

In this known method, the regulation to prevent the formation of condensate is limited to the distribution of the amount of oil that is sent to the cooler and the amount of oil that is directly injected into the compression element without cooling.

Another method, known from (OV 2.394.525|), in which the thermostatic valve ensures that the temperature of the injected oil does not fall below the set value, and at the same time, additionally uses a thermostatically adjustable valve that regulates the amount of injected oil in depending on the temperature of the injected oil.Both adjustments are performed simultaneously and independently of each other and other adjustments.

The purpose of this invention is to provide a solution to at least one of the above-mentioned and other disadvantages.

The subject of this invention is a method of regulating an oil-injected compressor device, which has at least one compression element with an inlet for gas for compression and an outlet for compressed gas and a regulator that can change the speed, for which the compressor device has an oil circuit with an oil separator with an inlet , which is connected to the output of the compression element, and the output to which the compressed gas can be connected to the consumer's network, and this oil separator has a reservoir under pressure in which the oil separated from the compressed gas is received, and from which the oil can be directed to the cooler, and then can be injected into the compression element, and this cooler is cooled by a refrigerant that is directed through the cooler by a fan or pump, with the characteristic that the bypass pipe for oil is installed on the cooler, due to which, the method consists in determining the temperature at the outlet from of the compression element and when this temperature is determined to be lower than the set value operation, the following operations are performed sequentially: - first, the fan or pump is turned off or its speed is reduced until the temperature at the outlet becomes lower than the preset value, and the minimum speed of the fan or pump is not reached; - then the temperature at the outlet of the compression element is determined again and, if this temperature at the outlet is still less than the preset value, oil is passed through the bypass pipe to the compression element or an increasing part of the oil is passed through the bypass pipe to the compression element until the maximum amount of oil is reached, - then, when the maximum amount of oil that passes through the bypass pipe to the compression element is reached, the temperature at the outlet of the compression element is determined again, and when this temperature at the outlet is less than the preset value, then the amount of oil that is injected into the compression element, reduced until the outlet temperature is at least the preset value or the minimum oil quantity is reached.

The advantage is that this method will prevent the temperature of the compressor device, which becomes too low, since the implementation of the method will lead to a gradual decrease in the cooling capacity of the oil circuit, by implementing various sequential adjustments step by step.

In this way, it is possible, for example, to prevent the formation of condensation.

This method is very convenient for use in a compression element that has a controlled intake throttle valve.

When such a compression element rotates at a reduced or minimum speed, the inlet throttle throttles the inlet so that less power is required by the compression element and using this method will ensure that the temperature does not become too low.

The minimum flow rate obtained in this way, when using a compressor device with adjustable speed, can be reduced due to the use of an inlet throttle valve without the risk of condensation and all the harmful consequences of this.

An added benefit is that the fan or pump is turned off or regulated first when cooling capacity is needed, and less energy is consumed.

Another advantage is that the oil supply is reduced only at the last operation, so the lubrication of the compression element with oil is not endangered.

Similarly, the method according to the invention provides regulation. outlet temperature, in order to ensure that this temperature does not become higher than the set value, for this, the following operations are performed in sequence: - first, the amount of oil injected into the compression element is increased until the set value of the temperature and the maximum amount of injected oil will not be achieved; - then, when the maximum amount of oil injected into the compression element is reached, the outlet temperature is determined again and, when this temperature is still higher than the set value, the oil is passed through the cooler to the compression element; - then, the temperature at the outlet of the compression element is determined again and, when this outlet temperature is still higher than the set value, the fan or pump is turned on or its speed is increased.

In order to better show the features of this invention, several preferred variants of the implementation of the method, according to this invention, for regulating the compressor device with oil injection, which does not have any restrictive nature, are described below as an example, with references to the attached drawings, where: in Fig. 1 schematically shows an oil injection compressor device for use in the method of the present invention; 60 in fig. 2 schematically shows a possible embodiment of the inlet throttle valve.

The compressor device 1 with oil injection (Fig. 1), in fact, contains a compression element 2, in this case a known screw type with a housing 3, in which two coupled spiral rotors 4 are driven by a regulator 5 to change the speed.

It is clear that the compression element 2 can also be of a different type, for example a turbocompression element, without going beyond the scope of the invention.

In this case, this speed regulator 5 is a motor b, the speed of which is variable.

The housing C has an inlet 7 which is connected to an inlet pipe 8 for supplying gas for compression, for example air or another gas or a mixture of gases.

The body C has an outlet 9, which is connected to the exhaust pipe 10.

The outlet pipe 10 is connected, through the reservoir 11 under the pressure of the oil separator 12 and the pressure pipe 13 connected to it, to the downstream network of consumers for supply to various pneumatic tools or the like, which are not shown.

The compressor unit 1 is provided with an oil circuit 14 to inject oil 15 from the pressure tank 11 through the feed pipe 16 and the pressure oil pipe 17 into the compression element 2 for cooling and, if applicable, for lubrication and/or sealing between the rotors 4 mutually and between the rotors 4 and the body 3.

The oil 15 that is injected can thus pass through the cooler 18 to cool the oil 15 from the reservoir 11 under pressure.

In this case, the cooler 18 is equipped with a fan 19 for cooling, although it is possible that instead of using cooling air for cooling, a liquid refrigerant is used, which is sent through the cooler by a pump. In this case, but not necessarily, the fan 19 is a controlled fan, that is, the speed of the fan 19 can be adjusted.

According to the invention, the oil 15 can also be directed to the compression element 2 through the bypass pipe 20, as a result of which in this case the oil 15 does not pass through the cooler 18.

In this case, a three-way valve 22 is provided on the outlet pipe 21 of the bypass pipe 20, upstream of the cooler 18, to regulate the amount of oil 15 that can flow through

From the bypass pipe 20 and through the cooler 18.

It is clear that it is also possible to adjust other than the three-way valve 22.

In addition, a means is provided for the possibility of adjusting the amount of oil 15 that is injected into the compression element 2, for example, in the form of an injection valve 23 in the discharge pipe 17, or by an appropriate selection of the diameter of the pressure pipe from a series of available diameters.

In this example, an intake throttle valve 24 is provided in the intake pipe 8.

In this case, as an intake throttle valve 24, an intake valve is used, which has a body containing a diaphragm 25 in the form of a row of petals 26, which are movably mounted in the body, and the petals 26 are installed with the ability to move between the closed position when the petals 26 close the intake pipe 8, and in the open position when the petals 26 are deflected from the intake pipe 8. A possible embodiment of such an intake valve with a diaphragm 25 is shown in fig. 2. It is obvious that such an inlet valve can be made of different designs.

The advantage of such an intake valve is that the petals 26 can be completely deflected from the intake pipe 8, and thus the inlet 7 is open, that is, in the open state, the diaphragm 25 does not form an obstacle to the supply of air for compression.

This is in contrast to, for example, a rotary valve, in which even in the fully open state there will be a partial overlap of the passage in the intake pipe 8.

The compressor device 1 with oil injection also has means 27a for determining the temperature T at the outlet 9 of the compression element 2 and means 275 for determining the pressure p in the pressure pipe 13. These means 27a and 275, respectively, can be, for example, a temperature sensor or a pressure sensor.

In addition, in this case there is also a regulator 28 that provides control of the engine 6, the fan 19, the three-way valve 22, the injection valve 23 in the injection pipe 17 and the intake throttle valve 24. The regulator 28 is also connected to the temperature sensor and the pressure sensor.

The operation of the compressor device 1 and the method according to the present invention for controlling it are very simple and are as follows.

During the operation of the compressor device 1, the compression element 2 will compress the gas entering through the inlet pipe 8.

In order to guarantee the good operation of the compression element 2, oil 15 must be injected into the compression element 2. This oil 15 is injected into the compression element 2 through the feed pipe 16 and the discharge pipe 17 under the influence of the pressure in the tank 12.

The compressed gas is sent to the tank 11 under pressure from the oil separator 12 through the exhaust pipe 10.

The oil 15, which is present in the compressed gas, is separated in the oil separator 12 and collected in the tank 11 under pressure.

The compressed gas, which is now free from oil 15, is supplied to the consumer network through the pressure pipe 13.

In order to ensure a satisfactory compressed gas pressure in the consumer network, the pressure P downstream of the output 29 of the oil separator 12 is determined by a pressure sensor.

The signal from the pressure sensor is read by regulator 28.

The regulator 28 regulates the compressor device 1, more specifically the engine b and the inlet throttle valve 24, so that the flow of the required speed enters the compression element 2 to maintain the pressure P downstream of the output 29 of the oil separator 12 of the desired Rzei value.

In this case, it is carried out by the following adjustment of the engine b and the intake throttle valve 24.

When the pressure P is less than the desired value Rzei, in other words, when the consumption of compressed gas is greater than the flow rate supplied by the compressor device 1, the regulator 28 will ensure that the supplied flow rate becomes greater by gradually opening the inlet throttle valve 24 in the first case, if it throttles input 9 at this time until the pressure P again reaches the desired value Rzei.

When the pressure P is still less than the desired value Rzei, when the inlet throttle valve 24 is fully open, the regulator 28 will gradually increase the speed of the compression element 2 so that the flow rate supplied by the compression element does not rise to the pressure P downstream of the inlet 29 of the separator 21 oil will not reach the desired Rzei value.

This means that at this time the demand for compressed gas is equal to the supplied flow rate.

When the pressure P is greater than the desired value Rzei, in other words, when the consumption of compressed gas is less than the flow rate supplied by the compressor device 1, the regulator 28 will ensure that the flow rate supplied is reduced by gradually reducing the speed of the compression element 2 in the first case so that the flow rate supplied by the compression element 2 will fall until the pressure P is again equal to the desired value of Rzei.

When the pressure P is still higher than the desired value of Rzhea, when the minimum speed is reached, the regulator 28 will gradually close the inlet throttle valve 24 until the pressure P at the outlet 29 of the oil separator 12 reaches the desired value of Rzhea.

The intake throttle valve 24 must be closed to the minimum opening. When the pressure

P is still too large, regulator 28 stops the compression element. The inlet throttle valve 24 will then also be fully closed to prevent air and oil from flowing in the opposite direction.

When the compressor unit 1 is started again, the compression element 2 will operate at the minimum speed and the inlet throttle valve 24 will be opened to the minimum.

The regulator 28 will then gradually open the intake throttle valve 24 in order to limit the starting torque of the engine 6. Only the intake throttle valve 24 was fully open, then the speed of the compression element will be increased.

The advantage of this adjustment of the pressure P at the outlet 29 is that the inlet throttle valve 24 is kept as open as possible. Finally, when the flow rate is to be reduced, the speed of the compression element 2 will first be reduced before the inlet throttle valve 24 is adjusted, and when the flow rate is to be increased, the inlet throttle valve 24 will first be opened, if it has not been fully opened so far.

Due to the use of the inlet throttle valve 24 in combination with control with variable speed regulation, a drop in temperature T at the outlet 9 of the compression element is possible. 2, when the compression element 2 is driven at minimum speed and the input 7 is throttled.

As long as there is a high demand for compressed gas, the inlet throttle valve 24 will be fully open and the compression element 2 will operate at maximum speed. In this case, the regulator 28 will control the oil circuit 14 in such a way that the cooling capacity 60 is maximum, namely:

- the injection valve 23 is fully open, so that the entire flow of oil is injected; - all the oil 15 will flow through the cooler 18; - fan 19 will work at maximum speed.

But, if the required flow rate drops sharply, the speed of the compression element 2 will decrease to the minimum speed and additionally the inlet throttle valve 24 will throttle the input 7 of the compression element 2 to adjust the flow rate delivered to the required speed.

As a result of this, the power required by the compression element 2 will be reduced, and therefore, accordingly, the temperature T.

In order to solve the problems associated with this drop in temperature, such as, for example, the formation of condensate, the regulator 28 according to the invention will regulate the compressor unit 1 as follows:

When the temperature T falls below the preset value T5ei, in the first case, the speed of the fan 19 is gradually reduced. If this is not enough, because the temperature T, after stabilization or after the expiration of the set time, remains too low, the fan 15 will be permanently switched off.

If a fan type 19 is used, the fan is turned off immediately.

The above-mentioned preset value of T5ei is preferably at least equal to the condensation temperature Tc, which is preferably increased by a certain amount, and Tc can. have a fixed value or can be a value that is calculated based on measured ambient temperature, relative humidity and operating pressure or that can be estimated based on several assumptions.

This will provide additional security to prevent condensation. This particular value of temperature can be at least 190 C, or at least 59 C, or at least 102 C, or as a last resort also from 09 C, if the operation will be at the safety limit.

This will depend on the level of special safety that is desired to prevent condensation in compressor unit 1.

Then, when the temperature T at the outlet 9, after stabilization or after the expiration of a certain time, is still below the preset value of T5, the regulator

From 28 will adjust the three-way valve 22 so that at least part of the oil flow is passed through the bypass pipe 20, and through the cooler 18. The oil 15, which passes through the bypass pipe 20, will not be cooled, so the cooling capacity of the oil circuit 14 will decrease.

If necessary, the regulator 28 will ensure that an increased portion of the oil flow will be supplied through the bypass pipe 20 to allow the cooling capacity to decrease and the temperature T will increase to a temperature above the preset value T5ei.

When all the oil is passed through the bypass pipe 20, and the temperature T, after stabilization or after the expiration of the set time, is still too low, then the regulator 23 will allow a reduction in the cooling capacity by adjusting the injection valve 23 in the discharge pipe 17 so that the amount of oil 15, which is injected, decreases.

The amount of oil 15 will be reduced until the temperature T is at least equal to the preset value T5ei to prevent condensation.

By using an adjustable fan 19 or, if possible, an adjustable pump and oil circuit 14, through which the oil 15 can be passed through the bypass pipe 20 and partially through the cooler 18, the cooling capacity can be continuously adjusted without the amount of oil 15 being injected for further change for this purpose.

In addition, only in the latter case, the amount of sprayed oil 15 is reduced so that the lubrication and sealing between the rotors 4 and/or the rotors 4 and the housing With oil 15 does not decrease.

Obviously, the method described above can be applied not only when the intake throttle valve 24 throttles the inlet 7 of the compression element 2, but also at any other time when the temperature T is below the preset value T5ei, even if the intake throttle valve 24 is not throttling inlet 7 or even if there is no throttling valve in the case of a variable control compressor unit.

A similar regulation can also be applied to ensure that the temperature T at the outlet 9 does not become higher than the set value T5ei. This adjustment can be applied alone or in combination with the temperature adjustment described above

T5ey.

This set value of Tmax is limited by the I5bO standard and its maximum value is equal to, for example, the destruction temperature of Ta oil 15. In application, the set value of Tmax can be several degrees less than the destruction temperature of Ta, to ensure a certain safety, for example, by 190, 50Sb or 109C, depending on the level of additional security that is desired or required.

For this purpose, the controller 28 determines the temperature T at the outlet 9 and if it is higher than the set value Titah, the controller 28 will adjust the injection valve 23 to increase the amount of oil 15 that is injected until the temperature T at the outlet 9 decreases to the set value Ttah.

If the maximum amount of oil 15 is already injected, or if the temperature T at the outlet 9, after stabilization or after the expiration of the set time, is still too high when the maximum amount of oil 15 is injected, then the controller 28 will perform the following operation to increase the cooling capacity.

The next operation consists in adjusting the three-way valve 22 so that at least part of the oil flow is passed through the cooler 18.

If this has already happened or if this is not enough, then the regulator 28 will ensure the gradual passage of most of the oil flow through the cooler 18 until the temperature T drops sufficiently.

When it turns out to be necessary to pass the entire flow of oil through the cooler 18 and the cooling capacity is still insufficient so that the temperature T drops to the set value Ttah, after stabilization or after the set time, the next adjustment by the regulator 28 will begin.

The controller 28 will turn on the fan 19 or pump, if applicable, thereby increasing the speed.

As a result, the oil 15 in the cooler 18 will cool more.

The speed of the fan 19 is increased until the temperature T at the outlet 9 reaches, at the maximum, the level of the set value Ttah.

By combining both methods of temperature regulation T, it is possible to guarantee that the temperature

T will be kept within certain limits to increase the durability of the oil 15 and the compressor unit 1.

In addition, this method ensures that the fan 19 or the pump will always be the first to be turned off or the last to be turned on when the cooling capacity of the oil circuit 14 must be reduced or increased, which will allow for energy savings.

The present invention is by no means limited to the variants of implementation described as examples and shown in the drawings, but such a method according to the invention, intended for regulating a compressor device with oil injection, can be implemented according to various variants without going beyond the scope of the invention.

Claims (13)

FORMULA OF THE INVENTION 1. A method of regulating a compressor device (1) with oil injection, which has at least one compression element (2) with an inlet (7) for gas to be compressed and an outlet (9) for compressed gas and a regulator (5) with variable speed, and the compressor the device (1) has an oil circuit (14) with an oil separator (12) with an inlet connected to the outlet (9) of the compression element (2) and with an outlet for connection to the compressed gas network for consumers, and this separator (12) of oil has a reservoir (11) under pressure for collecting oil (15) separated from the compressed gas and directing the oil (15) from it to the cooler (18) and then injecting it into the compression element (2), while this cooler (18) is cooled by a refrigerant that is directed through the cooler by a fan (19) or a pump, which is characterized by the fact that a bypass pipe (20) for oil (15) is installed on the cooler (18), and the temperature (T) at the outlet is determined ( 9) of the compression element (2) and, when this determined temperature (T) is lower than the previously set of the updated value (Т5ей), the following operations are successively performed: - first, the fan (19) or the pump is turned off or its speed is reduced until the temperature (Т) at the outlet (9)U becomes lower than the preset value (Т5ей) , and the minimum speed of the fan (19) or the pump is not reached; - then, the temperature (T) at the outlet (9) of the compression element (2) is determined again and, if this temperature (T) at the outlet (9) is still lower than the preset value (T5ei), the oil (15) is passed through the bypass pipe (20) to the compression element (2) or the increasing part of the oil (155) is passed through the bypass pipe (20) to the compression element (2) until the maximum amount of oil (15) is reached, - then, when the maximum amount of oil that passes through the bypass pipe (20) to the compression element (2) is reached, the temperature (T) at the outlet (9) of the compression element (2) is determined again, and when this temperature (T) at the outlet (9) is lower than before set value (T5ei), then the amount of oil (15), which is injected into the compression element (2), is reduced until the temperature (T) at the outlet (9uU) is at least equal to the preset value (Tzei) or the minimum amount of oil is not reached. 2. The method according to claim 1, which differs in that after each of the above consecutive operations, the next operation is performed only after the temperature (T) at the outlet (9) of the compression element (2) stabilizes or after the set period of time has expired. C. The method according to claim 1 or claim 2, which is characterized in that the compression element (2) has an adjustable inlet throttle valve (24) and that at least when the inlet throttle valve (24) throttles the inlet (7) of the compression element (2), perform the above operations. 4. The method according to any of the previous points, which differs in that, when the temperature (t) at the outlet (9) is higher than the preset value (Ttah), the following sequential operations are performed: - first, the amount of oil ( 15), which is injected into the compression element (2), is increased until the set value (Tmax) of the temperature and the maximum amount of injected oil are reached; - then, when the maximum amount of oil (15) injected into the compression element (2) is reached, the temperature (T) at the outlet (9) is determined again and, when this temperature (T) is still higher than the set value (Tmax) , oil (15) is passed through the cooler (18) to the compression element (2); - then, the temperature (T) at the outlet (9) of the compression element (2) is determined again and, when this temperature (1) at the outlet (3) is still higher than the set value (Ptah), the fan (19) or the pump is turned on or its speed is increased. 5. The method according to claim 4, which differs in that after each of the above consecutive operations, the next operation is carried out only after the temperature (T) at the outlet (9) of the compression element (2) has stabilized or after the set period of time has expired. 6. A method according to any of the previous items, characterized in that the fan (19) or the pump is an adjustable fan (19) or pump, the speed of which can be adjusted, whereby, during the switching operation, the fan (19) or the pump , the speed of the fan Zo (19) or the pump is gradually reduced, and when the temperature (T) at the outlet (9) becomes lower than the set value (Tzeei), the fan (19) or the pump is turned off and/or during the operation of turning on the fan (19 ) or pumps, the speed is gradually increased until the temperature (T) at the outlet (9) becomes the maximum, which is equal to the set value (Tmax). 7. The method according to any one of the preceding points, which is characterized by the fact that the oil circuit (14) is designed in such a way that the oil (15) can be partially directed through the bypass pipe (20) and partially through the cooler (18), through that, during the operation of passing oil (15) through the bypass pipe (20), the following sub-operations are performed: - at least part of the oil flow is passed through the bypass pipe (20); - then, when the temperature (7) at the outlet (9) of the compression element (2) is still lower than the preset value (Tz5ei), then most of the oil flow is gradually passed through the bypass pipe (20); and/or because of which, during the operation of passing oil (155 to the compression element (2) through the cooler (18), the following sub-operations are performed: - at least part of the oil flow is passed through the cooler (18); - then, when the temperature (T) at output (9) of the compression element (2) is still higher than the set value (Tmax), then most of the oil flow is gradually passed through the cooler (18). 8. The method according to any one of the preceding points, which is characterized by the fact that the preset value (Tzei) is higher than the condensation temperature (Ts) by a certain amount. 9. The method according to claim 8, which is characterized by the fact that the preset value (Tzei) is at least 0 "C, more preferably at least 1 "C, even more preferably at least 5 "C or at least 10 "C. 10. The method according to any one of the previous items 4-9, which is characterized by the fact that the set value (Ttah) is maximally equal to the destruction temperature (Ta) of the oil (15) or the value determined by the I5BO standard. 11. The method according to any one of the preceding points 3-10, which differs in that it has the operation of determining the pressure (p) at the output of the oil separator (12), due to which one of the following operations is performed: - when the pressure (p) at the output of the oil separator (12) is higher than the desired value (rze), the speed of the compression element (2) is gradually reduced and, if possible, the inlet throttle valve (24) is also gradually closed until the above-mentioned pressure (p) is equal to the set value ( rgei); - when the pressure (p) at the outlet of the oil separator (12) is less than the desired value (rg), the inlet throttle valve (24) is gradually opened and, if possible, the speed of the compression element (2) is increased until the above-mentioned pressure (p) will be equal to the set value (rge)). 12. The method according to any one of the previous items 3-11, which is characterized in that as an intake throttle valve (24) an intake valve is used, having a body that accommodates a diaphragm (25) in the form of a row of petals (26), which movably fixed in the housing, and the flaps (26) are made with the possibility of movement between the closed position, in which the flaps (26) cover the inlet (7) of the compression element (2), and the open position, in which the flaps (26) are deflected from the inlet (7) ). 13. The method according to any one of the previous items, which is characterized in that the compression element (2) is a screw compression element. 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